Read this Uber exec’s heartfelt resignation letter by Ben Geier @FortuneMagazine March 17, 2015, 9:28 AM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons Uber CFO Brent Callinicos resigned this week, and the note he sent to his colleagues at the startup is fairly emotional. The move echoes Google Chief Financial Officer Patrick Pichette’s recent good-bye note. Callinicos starts by quoting philosopher John Dewey, and then gets right into the reason why he’s leaving: Time has a way of passing quickly, easily leaving your heart’s desire to “maybe happen later.” For me, there is no later. It is now. It is time to do what I have desired for a very long time; time to keep a promise to my wife of not missing another school play, swim meet, or academic achievement of our daughter’s childhood. Time; time; time, to encapsulate what matters most to me; time, to admit that every day I work, I lose time with my family; time, to help my daughter understand how important time is before time becomes a blur to her too. It is simply time. Uber CEO Travis Kalanick also sent a note about Callincicos’ leaving, in which he praised the CFO for helping get Uber to where it is today: Almost 2 years ago, I brought on one of the great financial operators in Silicon Valley as our CFO. Though two years sounds short, Uber was a much smaller startup then – about 1/10th the size we are today. Brent has provided critical leadership to take Uber to the next level as we matured as a company. We have financial systems in place overseeing operations in 53 countries. We have a deep bench of talent poised to help our finance organization grow with the business. Read both letters in their entirety at the Wall Street Journal.